This invention relates to a fixing mechanism for a stair unit which can assemble a curved stair without the necessity of support poles.
The inventor of the present invention previously proposed a stair unit (Japanese Patent Application No. 163010/1980) having the following construction. As shown in FIGS. 1 and 2, two cylindrical members 1, 2 are juxtaposed in the spaced-apart relation in the vertical direction, and an element 3 having a flat upper surface 3a is supported and fixed so that the upper surface 3a crosses at right angles the axes Y and Y' of the two cylindrical members 1 and 2. The cylindrical member 1 projects upward beyond the element 3, while another member 2 projects downward from the element 3. The outer diameter of the upwardly projecting cylindrical member 1 is considerably smaller than the inner diameter of the member 2 so that both cylindrical members 1, 2 can be fitted to the corresponding cylindrical members 2, 1 of another stair unit (not shown).
After the stair unit 4 of the type described above is fitted into the cylindrical members of another unit as shown in FIG. 3, both stair units are adjusted so as to attain a predetermined angle and height (h) and are then fixed together via a fixing mechanism (not shown). The same procedures are repeated to complete a curved stair. Incidentally, reference numeral 5 represents a tread, 6 is a floor board and 7 is an upper unit to be fitted to the floor board 6.
On the other hand, the stair fitting position and the distance between a lower floor and an upper floor vary from building to building. In order to have the stair unit wide spread, therefore, a fixing mechanism which can easily adjust the height and angle displacement between the stair units must be developed by all means.
The inventor of this invention proposed previously a fixing mechanism to satisfy the technical requirement described above (Japanese Patent Application No. 68885/1981). The fixing mechanism comprises two lines of round apertures 10 bored in parallel and symmetrically with one another on an upwardly projecting cylindrical member 1, rivet-like pins 11 slidably fitted into the round apertures 10, a conical base 13 having a bolt shaft 12 implanted and fixed vertically onto its axis, a conical base 14 fitted on the upper end of the bolt shaft 12 can penetrate through, and a nut 15 mating with the bolt shaft 12. After the conical bases 13, 14 are arranged so as to oppose each other between the two lines of round apertures 10, the nut 15 is fastened so that both conical bases 13, 14 come close to each other, the pins 11 are pushed outward in consequence and the outer ends of pins 11 are brought into pressure contact with the inner circumferential surface of another cylindrical member 2, thereby fixing the upper unit 4 and the lower unit 4 with each other.
The fixing mechanism described above can certainly adjust the height and can change the angle displacement, but since the cylindrical members 1, 2 are fixed while they are fitted and kept floating, fixing is troublesome and fine adjustment of the height and angle displacement is difficult between the stair units.
The fixing mechanism involves also the following problem in the assembly work. In other words, the assembly is started either from an upper unit 7 that is fitted to the floor board 6 of the second floor or from a lower unit (not shown) that is fitted to the floor board of the first floor, and when the assembly is started from the upper unit, a support means for temporarily supporting each stair unit 4 is necessary in order to prevent the fall of each stair unit 4.